This project will study the concentration dependence of the effects of selected, commonly used insecticides on several membrane transport phenomena. Included will be studies of Na, K ion, and Ca ions transport and Na-K ATPase activity. Four different preparations will be used: isolated frog skin, human erythrocytes, isolated electroplaques of electric eels, and isolated giant axons of lobster. The involvement of protein sulfhydryl groups will be examined. It is expected that the results will help to elucidate the mechanisms by which insecticides alter membrane phenomena and also improve our understanding of normal membrane function.